Cells were dual cross-linking with a mixture of 2 mM each of ethylene glycol bis (succinimidyl succinate) (EGS) and disuccinimidyl glutarate (DSG) and 1% formaldehyde. Chromatin was digested with 60 units MNase (New England Biolabs, M0247S) at 37 0C for 10 minutes and then sonicated using Branson Microtip Sonifier 450 (4X15 second at output 4.5 and duty cycle 60%) to the sizes mostly between 150-500 bp. 50 μg chromatin, antibodies for transcription factors (listed in Table S6), and 15 μl Dynabead protein G (Thermo Fisher Scientific, 10004D) was used for the chromatin immunoprecipitation (ChIP)